Portable cooling devices for cooling foods or beverages, such as self-contained beverage cans that cool their contents at the press of a button, are well known in the art. Typically, the beverage can will contain either: a) two chemicals separated by a breakable membrane that are endothermically reactive; or b) a container of a high pressure liquid or gas expandable through a breakable valve such that vaporization or Joule-Thomson expansion, or both, causes a refrigeration effect.
One problem with the present refrigerant-based designs is that the refrigerant is exhausted into the atmosphere. Therefore, the refrigerant should be nontoxic, chemically stable, and environmentally friendly. A refrigerant that meets these requirements is carbon dioxide; however, liquid carbon dioxide has an excessively high vapor pressure at room temperature, which requires a heavier container and causes more consumer risk.
Another problem with both present designs (chemical reactants and refrigerants) is that they are not reusable. Once the chemicals have endothermically reacted, or once the refrigerant has expanded, the process cannot be repeated.